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Jul 1, 2007

Anyone for a Knob Wheel?

Despite these wheels being in the education kit, the retail kit and the education resource set, I don't see them used in many models. That could be because I don't get out much, or it could be that their slipperiness makes them less suitable than conventional gears. (I used them in pairs while building Alpha Rex, but the knobs kept disengaging from each other).

Knob wheels provide more surface contact than a regular gear, hence more torque (theoretically). But I haven't seen many around.

Can anyone point us to models on the web or in NXTlog that use these wheels? They look too good to just lie in the box.

They work very well when you want a lot of torque to go through a 90 degree bend without teeth slipping. I use them quite a lot. For example in my NXT roadster at http://mrmandrake.wordpress.com/2007/01/27/nxt-roadster/ . If you look at the picture of the underside at the bottom of the page you will see how I used them for the steering and to link to the engine's chain drive.

See my transmission car for a good use of these: http://www.tau.ac.il/~stoledo/lego/ShiftingGears/

To shift gears, I needed toshift the angle of rotation by90 degrees, and bevel and crowngears just kept slipping. Theywere not able to transfer enoughtorque. The knob gears do agreat job here without slipping.

Another useful application of these is gearing at *arbitrary* angles, not just as spur gears (no change in axle angle) or crown/bevel gears (90° shift in axis). With the odd angles that are possible under studless design, I suspect this may be used more frequently.

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